1. Field of the Invention
This invention relates to a camera having a detachable viewfinder and a visual line detection device that enables the detection of the visual line of the photographer as the photographer looks through the detachable viewfinder, and that enables one to set the camera for various types of photographic conditions.
2. Description of Related Art
Japanese Laid-Open Patent Application No. 1-274736 discloses a camera having a visual line detection device. With this camera, illuminated is the eyeball of the photographer looking through the viewfinder by a light beam, and images of the photographer's eyeball and light reflected from the cornea are focused on a CCD (charge coupled device) area sensor by means of a light concentrating lens. The central position of the pupil and the incidence position of the reflected light are obtained from these images. By calculating the rotational angle of the eyeball, a determination can be made as to which region of the viewfinder and, thus, which portion of the object image the photographer is viewing.
Other documents disclosing visual line detection devices include U.S. Pat. No. 4,836,670, U.S. Pat. No. 4,950,069, U.S. Pat. No. 5,036,347 and U.S. patent application Ser. No. 08/005,829.
The size of the eyeball and its visual axis, and whether it be the naked eye, one that is fitted with a contact lens, or if glasses are worn, will vary with each photographer. Hence, when calculating the visual line of the photographer, such individual differences are often ignored, making it easy to err in the calculation of the visual line by making use of calculations that rely on average values. Hence, with the camera that is fitted with the visual line detection device disclosed in the above-identified Japanese Laid-Open Application No. 1-274736 and U.S. patent application Ser. No. 08/005,829, data relating to the eyes of the individual photographer (referred to as "calibration data") is pre-input into the camera, in order to suppress an occurrence of errors in calculations.
It is well known to use different types of viewfinders (which are interchangeable with the camera body) in single lens reflex cameras. However, when visual line detection devices also are included in single lens reflex cameras having interchangeable viewfinders, if adaptation is made for providing a memory storage device into which the calibration data are stored in the camera body, there is a loss of reliability when the viewfinder is changed. Accordingly, new values for the calibration data must again be input to the camera body after changing the viewfinder.